This invention relates to apparatus for automatically applying, as by rubbing or spraying, a liquid agent to the surface of an article to be tested and for wiping, if necessary the applied liquid agent, and more particularly to an apparatus for automatically applying, as by rubbing or spraying, a plurality of liquid agents in optimum amounts to the surface of an immovable structure when a non-destructive test for detecting defects in the structure is carried out and for wiping these liquid agents, if necessary, from the surface of the structure.
Generally, difficulties are encountered in detecting, by naked eyes, fine fissures or pinholes on the surface of an article. It is common practice to use a variety of non-destructive testing methods for detecting the presence or absence of surface defects in a tested article. Of all the non-destructive testing methods, a penetration test for detecting defects has hitherto been widely used, because this method is relatively easy to practice and yet capable of detecting defects with a relatively high degree of precision.
In carrying out the penetration test for detecting defects, a penetrating liquid is applied, as by rubbing or spraying, to the surface of an article to be tested so as to cause the penetrating liquid to find its way into defects, for example, and then the penetrating liquid applied to the surface of the article to be tested is wiped, or the surface of the article coated with the penetrating liquid is dried and a finishing liquid is applied to the surface. In this way, defects on the surface of the article to be tested are colored and recognized by naked eyes.
It has hitherto been customary to apply the penetrating liquid and finishing liquid manually, when the penetration test for detecting defects is carried out. Therefore, this testing method has not hitherto been carried out satisfactorily when there are many surfaces to be tested. Manual application of liquids to a lot of surfaces is carried out only with low efficiency. Moreover, when liquid application is carried out manually, it is impossible to equalize the amounts of liquid applied to various surfaces, and there is a tendency to apply the liquid in an amount which is greater than is necessary.
A penetration test for detecting defects has been described in U.S. Pat. Nos. 3,762,216, 3,926,044 and 3,341,010, Japanese Patent Application Laid-Open No. 15591/75 and Japanese Patent Publication No. 34623/74, for example. The apparatus disclosed in the prior art for carrying out this testing method are all intended for use in movable structures or articles. These apparatus are not adapted for use in testing immovable structures, or a great difficulty is experienced in applying these apparatus to the testing of immovable structures. Moreover, these apparatus have the disadvantage that the amount of the liquid applied to the surface of a structure to be tested sometimes becomes too great, because the liquid is applied by spraying through nozzles and other means to the surface to be tested, with the result that the consumption of the penetrating liquid is high. Another problem encountered with regard to the apparatus of the prior art is that, when the liquid is applied in excess to a portion of a surface from which excess liquid cannot be removed, the liquid collects in this portion and means must be provided for removing excess liquid from this portion in order to efficiently carry out the test.